Concrete mixes are changing. Governments and the concrete industry are pushing for lower carbon cement and mixes, and some public projects now require them. For builders, concreters and formworkers, this can mean different setting times, strength gain and paperwork on site.
Why concrete is the focus
Most of the carbon in concrete comes from making cement. The main ways to cut it are to use less ordinary cement and replace some of it with other materials. These include:
- Supplementary cementitious materials (SCMs): by-products such as fly ash from coal power stations and slag from steel making.
- Limestone cements: cement with more ground limestone blended in.
- Recycled materials: such as recycled concrete aggregate.
New Zealand and Australia
New Zealand: Concrete New Zealand members have committed to carbon-zero concrete by 2050. Their roadmap, last updated by BRANZ in June 2024, targets a 44 percent cut in direct and electricity-related emissions from 2020 levels by 2030. Steps before 2030 include more ground limestone and SCMs in cement and alternative fuels at cement plants.
Australia: New South Wales has a Low Carbon Concrete Requirement that can be written into project specifications. It offers two main pathways:
- Replace at least 50 percent of cement with SCMs on average, by weight.
- Or cut embodied carbon by at least 40 percent on average, compared with a standard Portland cement mix.
- At least 10 percent of total project concrete should use recycled concrete aggregate, crushed slag aggregate or geopolymer concrete.
- Contractors keep a concrete register recording each pour, the mix used and its SCM content.
These targets can be adjusted per project, and may be lower in regional areas where supply is limited.
United Kingdom, United States and Canada
- United Kingdom: The revised concrete standard, BS 8500, was welcomed by industry in December 2023. It allows a wider range of lower carbon cements, including new multi-component blends. In May 2026, the government said it will bring in a voluntary embodied emissions reporting framework for steel, cement and concrete.
- United States: Portland-limestone cement has a carbon footprint up to 10 percent smaller than standard Portland cement, according to the Portland Cement Association. By April 2024, every state transport department had approved its use. US Geological Survey data showed it overtook standard Portland cement in market share in June 2023.
- Canada: The federal Standard on Embodied Carbon in Construction applies to larger federal building projects. An update in July 2025 added requirements for whole-building life cycle assessments and for structural and reinforcing steel, on top of the earlier concrete rules.
What changes on site
The NSW government has published practical guidance on high-SCM concrete. Key points for crews:
- Early strength can be lower. SCMs dilute the cement, which can slow early strength gain, though long-term strength improves. This matters for formwork stripping and stressing times.
- Test before stripping early. The guidance recommends trials to understand strength gain, and maturity testing for large elements with more than 50 percent SCM.
- Curing matters more. Good early curing helps reduce higher carbonation rates seen in some high-SCM mixes.
- Workability can change. Suppliers can manage this with admixtures and mix adjustments.
- Placing temperatures are the same. The usual range of about 5 to 35 degrees Celsius applies, as for ordinary cement mixes.
- Slower setting can help. In hot weather and large pours, SCMs reduce heat build-up.
Cost and supply
According to the NSW guidance, high-SCM mixes typically cost 0 to 5 percent more. If the mix must match ordinary cement’s early strength, costs can rise by about 20 percent.
Supply is a real issue. Fly ash and slag supply can go up and down, and is under pressure as coal plants close and steel making changes. The NSW guidance suggests talking to suppliers four to five months ahead for Sydney projects and six to nine months ahead for regional projects.
What it means for your business
- Read the specification closely. Public projects may now set limits on cement content, SCM levels or embodied carbon.
- Ask your concrete supplier which lower carbon mixes they offer, how they perform, and how early you need to order.
- Plan for slower early strength. Allow more time before stripping formwork, or agree a mix designed for early strength.
- Keep good pour records. Some projects now require a register of every mix and pour.
- Price carefully. Lower carbon mixes can cost a bit more, especially when early strength is needed.
Sources
- Achieving a path to net-zero carbon concrete, BRANZ
- NSW Low Carbon Concrete Requirement guidance, NSW Government
- Low carbon concrete: frequently asked questions, NSW Government
- New British standard for concrete welcomed, Concrete Connect
- DESNZ publishes response to consultation on policy framework for low carbon industrial products, LexisNexis
- All 50 states give environmentally conscious cement the green light, Portland Cement Association
- Policy notice 2025-6: Standard on Embodied Carbon in Construction, Treasury Board of Canada Secretariat
This article is general information based on sources available in October 2026. Rules, prices and figures change, so check the current details with the official source where you work.